1. Field of the Invention
The present invention is related to a light emitting diode package and a lamp with the same, and more particularly to a light emitting diode package comprising a constant current circuit and a lamp with the same.
2. Description of the Prior Art
Having advantages of small volume, long life and low power, light emitting diodes (LED) have been widely applied for various illuminating and decorating purposes. A prior art direct current (DC) driven LED module requires a rectifying circuit or a power converter to convert an alternating current (AC) power source into a DC power source. Since a larger printed circuit board (PCB) is required for the rectifying circuit or the power converter, the DC driven LED module has a larger volume and is not suitable for a compact lamp, such as an E12 lamp base.
Another prior art AC driven LED module connects at least two LEDs in anti-parallel, and inserts a resistor between the LEDs and the AC power source. In such way, during the first half period of the AC power source, the LED with the same direction is driven, and during the second half period of the AC power source, the LED with the opposite direction is driven. As the circuit is simple compared to the DC driven LED module, the AC driven LED module has a smaller volume.
However, in order to prevent a surge from the AC power source to damage the LED, additional electronic elements such as resistors, capacitors are needed to limit the amount of current. Therefore, the volume of the AC driven LED module cannot be effectively reduced to a size suitable for a compact lamp. Also, the resistor of a high resistance causes a higher percentage of power to be dissipated into heat thereby incurring waste, and causes the luminous efficiency of the LED to be inferior because of the lower current. Moreover, since the amount of current varies with voltage, the brightness of the LED cannot be easily controlled effectively.
In summary, it is highly desirable to provide an LED module of a smaller volume and more stable current.